The royal natural history . nished with suckers, or hooks, or both, by meansof which the worm adheres to the walls of the intestine of the host it nervous system consists of a ganglion in the head, and a cord on each a well-known example, we may take Taenia saginata, one of the human tape-worms; and since its structure and the phases through which it passes in thecourse of its development are thoroughly known, a detailed discussion of itscharacteristics will serve as an introduction to the study of the group. In its 460 WORMS. mature state this worm, which spends this stage
The royal natural history . nished with suckers, or hooks, or both, by meansof which the worm adheres to the walls of the intestine of the host it nervous system consists of a ganglion in the head, and a cord on each a well-known example, we may take Taenia saginata, one of the human tape-worms; and since its structure and the phases through which it passes in thecourse of its development are thoroughly known, a detailed discussion of itscharacteristics will serve as an introduction to the study of the group. In its 460 WORMS. mature state this worm, which spends this stage of its existence in the humanintestines, may reach a length of 5 or 6 yards. Its head is relatively minute,being only about equal to that of an average pin in size, and furnished withfour suckers, by means of which the creature adheres firmly to the walls of theintestine. The head is followed by a narrow piece called the neck, which graduallypasses posteriorly into the trunk. It is not jointed, but where it merges with the. a nemertine, Pterosoma planum (enlarged). trunk it becomes marked by shallow grooves, growing deeper and deeper as theyrecede from the head, until ultimately they divide up the body into a chain offlattened, square or oblong segments, of which there may be many segment is called a proglottis, the whole series being termed muscular system is fairly well developed, and consists of fibres runninglengthwise throughout the segments and across from side to side, and of otherspassing from the upper to the lower walls. By means of these muscles the wormis able to shift at will its point of attachment to the gut, and to lengthen or FLAT-WORMS. 461
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectzoology
